The invention relates to a hydraulic control apparatus for an automatic dual clutch transmission, and to a method for controlling the transmission using the hydraulic control apparatus.
Dual clutch transmissions have long been known and are preferably used in motor vehicles. A dual clutch transmission generally has two partial transmissions, each of which are assigned a separate clutch and a set of gears. On account of the considerable mechanical outlay involved in actuating the two clutches and shifting the gears of the two partial transmissions, dual clutch transmissions are generally automatic, i.e. both the actuation of the clutches and the shifting of the gears are effected by associated auxiliary drives which, by way of example, may be designed in the form of hydraulically operated actuators which are actuated by a hydraulic control device.
Known hydraulic control apparatuses for dual clutch transmissions have generally complex control methods with a large number of valves. For example, it is known from DE 101 34 115 A1 for a first clutch and a second clutch each to be assigned a flow-regulating valve and for the actuators for shifting the gears each to be assigned a pressure-regulating valve. DE 41 17 736 C1 discloses providing a switching apparatus between a first and second pressure regulator, on the one hand, and the first and second clutch and the actuators for shifting the gears, on the other hand, with the result that a controlled pressure, generated by the pressure regulators, is passed either onto the clutches or onto one of the actuators. This switching operation allows the number of control valves required to be reduced compared to an arrangement as described in DE 101 34 115 A1, which provides a control valve for each of the clutches and for each of the actuators for engaging/releasing the gears.
In the case of the control apparatus described in DE 41 17 736 C1, only one pressure-regulating valve can be connected by the switching apparatus to the actuators for shifting the gears, while the other pressure-regulating valve can be connected only to either one clutch or the other. If one pressure-regulating valve fails, it is no longer possible to shift the gears.